What does Matthew 9:16 mean?

Jesus is answering a question from the disciples of John the Baptist, along with the Pharisees. They have asked why His disciples do not participate in regular fasting as they do (Matthew 9:14). Jesus is answering with three illustrations. First, He referred to wedding guests celebrating the presence of the groom (Matthew 9:15). This verse begins the second example.

Christ notes that nobody who was patching a torn garment would ever use a piece of unshrunk cloth. Natural fibers tend to shrink over time, especially after repeated washing and drying. Stitching brand new fibers over a hole in older cloth will eventually make the hole worse: the patch will shrink and pull away from the hole.

Whether His questioners understood it or not in the moment, Jesus is insisting that He is introducing something new. Judaism, especially as practiced by the Pharisees, is the "old cloth." As the Messiah and Son of God, Jesus had not come to fit into the old way of doing things under the Law. He had come to fulfill the Law (Matthew 5:17), by offering the grace of God. This grace is available to all who come to the Father through faith in Christ's death for their sin on the cross (John 3:16–18).

Even Jesus' own disciples did not yet fully understand. Nevertheless, the arrival of the king, the Messiah, on earth meant that the kingdom was near. Life in the kingdom would not be the same as it had been before the king arrived, even in its religious practices and observations.